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How do I get a body to be fixed on one of it's co-ordinates? So, for eg, something can still be knocked to the left and right, but not upwards or downwards (by gravity or another object)? Or both co-ordinates, but still able to rotate?
I know these are both used in that Phizix example, but there was far too much code in that for me to find what I needed, and the groups were named in a language I don't know (not a critisism, I just didn't understand it for obvious reasons).
* Always
> Set Body Y Position to ...
> Set Body Y Velocity to 0
Should work. Box2D has a prismatic joint for this purpose, but in chipmunk this is the only way I can think of.
If you want to lock both axises you could attach it to a static body using a pin joint.
Thanks Werbad, that works :D
However, I have a related problem (which is why I bumped this old thread). As there are multiple instances of an object to fix on an axis (and various levels will have varying numbers of instances), I don't know how to define which body I'm fixing. At the moment, I'm using the following code for initialisation of the object and fixing it:
Initialisation
Start Of Frame
-> Spread value 0 in SpreadID
Start Of Frame
-> Start loop "PushPlankInit"; NObjects("Plank") times
On Loop "PushPlankInit"
+SpreadID("Plank") = LoopIndex("PushPlankInit")
-> Set _YFix("Plank") to Y("Plank") <note: _YFix is Alt Val B>
-> Phizix: <body creation stuff, I won't bother typing it all as this bit works fine. Rotation is set to no rotation (-1)>
Fixing Y Co-ordinate
Always
-> Start Loop ("FixPlankY"); NObjects("Plank") times
On loop ("FixPlankY")
+SpreadID("Plank") = LoopIndex("FixPlankY")
-> Phizix: ActiveBodyID( "Phizix - Chipmunk Engine", Fixed( "Active" )) - Set Y Position to _YFix("Plank")
->ActiveBodyID( "Phizix - Chipmunk Engine", Fixed( "Active" )) - Set Y Velocity to 0
Now, this works fine except for one thing. When a different body collides with any plank other than the first instance, it moves straight through it rather than stopping (it does still push the plank slightly). Any idea what I've done wrong? I think it would be the Fixed("Active") bit, but I don't know what I should actually put there.
Regards,
~Raylax~
Now that's weird. I tried changing it to use ActiveBodyID in my Platform Movement Demo, and it does indeed mess things up. Try storing the body id in an alterable value of the object when you create it and use that instead. Have a look at the moving platforms in the Platform Movement Demo if you don't understand.
I think I know what you mean... would I change the last event in my previous post to:
On loop ("FixPlankY")
+SpreadID("Plank") = LoopIndex("FixPlankY")
-> Set Alt Value C("Plank") to ActiveBodyID( "Phizix - Chipmunk Engine", Fixed( "Active" ))
-> Phizix: Alt Value C("Plank") - Set Y Position to _YFix("Plank")
-> Alt Value C("Plank") - Set Y Velocity to 0
?
I'll give that a try, thanks :)
EDIT: Nope, that still has the weird glitch going off. I've probably misunderstood something x)
When you create the body, set a value of the active to LastBodyID, and use that value instead of ActiveBodyID.
Btw. You did attach the plank to the body right? I just realized I didn't in the platform demo...
Ah, I'll try that. And yeah, I'm pretty certain I attached it correctly. When the fix y events aren't there (ie, it acts as a normal free-falling body), it works fine.Quote:
Originally Posted by Werbad
Nope, that still doesn't work. One sec, I'll upload the file to the File Archive. I've probably missed something obvious x)
EDIT: Added file. http://www.clickteam.com/epicenter/ubbthreads.php?ubb=showflat&Number=116595#Post1165 95
Sorry to keep bumping the same old thread, but whilst my questions are still Phizix-related, I'd prefer to do that than keep creating loads of new ones. If it's more convienient to make a new thread each time for search purposes or whatever, then tell me and I'll stop using this old one =P
Anyway.
I'm putting this as a wall in my engine, but it doesn't react properly. I think I must have set up the "add custom vertexes" bit wrong.
http://img401.imageshack.us/img401/8...rgetileet3.png
That's zoomed to 400% it's normal size (it's normally 32x32), and the red dot indicates the centre point 16,16 (2 pixels to the right of that inside corner because of where the bricks have been sprited). These are the events to set up the shape of the brick (screenshotted because I'm too lazy to type):
http://img380.imageshack.us/img380/9850/setupgl3.png
Know where I've gone wrong?
Try the opposite order for adding the vertices? You've done anti-clockwise, they might need to be clockwise (it's more traditional to have vertices in clockwise order anyway).
You cannot use concave polygons!
http://en.wikipedia.org/wiki/Convex_polygon
The solution here would be to create 2 rectangle shapes.
With phizix, the shapes are supposed to be drawn counter-clockwise.Quote:
Try the opposite order for adding the vertices? You've done anti-clockwise, they might need to be clockwise
Fair enough.Quote:
Originally Posted by Nifflas
Convex vs Concave shapes it is then.
Ah, OK. Yeah, I'll make it as 2 rectangles then. Cheers :)
EDIT: Out of curiosity, why doesn't it work with concave polygons?